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What is fabric? what are the types of fabric? What is foliation?

                   


In structural geology, Fabric may be defined as the geometry arrangement of component features or fabric elements (such as mineral grains, clasts, compositional layers, fold hinges and planes of parting or some weak planes, etc.) seen on a scale large enough to include many samples of each feature. In sedimentary rocks, the texture created relies upon the depositional climate and can give data on current headings at the hour of statement. The texture might give data on both the direction and greatness of the strain that has influenced a specific piece of deformity rock.

On the basis of genesis, the fabric can be of two types-

1) Primary fabric: This is the fabric, which is formed during the formation of the rocks. For example, a preferred orientation of clasts long axes in a conglomerate, parallel to the flow direction deposition by a fast waning current. 

2) Tectonic fabric: This is the fabric, which is formed as a consequence of tectonic deformation. 

Based on the geometry of the fabric elements, the fabric itself can be categories into different groups such as –

1) Random: Here long axes of minerals are not parallel to each other. 

2) Preferred: Here long axes of elongate crystals are aligned parallel. 

3) Foliation: In foliation, fabric elements are planner and parallel. The first kinds of foliation feature that develop in a rock after depositions are called the bedding planes. In these bedding planes, we observed compositional variation. 

4) Lineation: Lineation is the geometry arrangement of the fabric elements like some parallel lines so that they are linear and parallel. 

5) Penetrative fabric: As the name suggests that the fabric, which is penetrating inside of the rocks that means if we break the rocks, then we found this fabric in the inner part of the rocks. Since the penetrative fabric is present throughout the rock, it is related to some kind of deformation, which is resulted in the alignment of the fabric elements so, the rocks, which are formed due to tectonic deformation such rocks, are termed as tectonites. If the tectonics show domination of foliation, then such tectonics are termed as S-tectonites. If we break S-tectonite rocks, then they have a tendency to split into sheets. If the tectonites show domination of lineation fabric, then such tectonites are called L-tectonites. If we break L-tectonite rocks, then they have a tendency to split into rods. If the tectonites show domination of strong foliation and strong lineation, then such tectonites are called L/S – tectonites. 

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